元古代北京裂谷槽中钾质碱性火山－深成作用

详细信息

PETROGENESIS OF POTASSIC ALKALINE VOLCANISM AND PLUTTONISM IN A PROTEROZOIC RIFT TROUGH NEAR BEIJING

摘要: 北京东部密云一平谷一带，受中元古代拉张性断裂控制，裂谷断陷区内的大红峪组钾质碱性玄武质与响岩质火山岩在时间及空间上与侵入相球斑花岗岩一辉绿岩共生。它们具有相似的板内碱性玄武岩和Ａ型花岗岩的同位素及地球化学特征。双峰式铁镁质及硅铝质岩浆是上地幔及下地壳更低程度部分熔融产物。

Abstract: Controlled by the Middle Proterozoic incipient rifting and extensional faulting,in the Miyun-Pinggu area of the eastern part of Beijing , potassic alkaline basaltic and phonolitic volcanic rocksof the Dahongyu Formation in the rift area are spatially and temporally associated with rapakivigranites and gabbro-diabase（anorthosite） intrusions. They display similarities to within-plate al-kaline basalt and A-type granite with respect to isotopic and geochemical characteristics, The bi- modal mafic and sialic magmas were derived by a low degree of fusion of the upper mantle andlower crust.